Biological fluids are routinely analyzed in hospital clinical laboratories to aid in the diagnosis of disease and to provide critical information about a patient's well being. The constituents of blood, lymph, urine or products derived therefrom provide meaningful information to a clinician about his or her patient's health. With physicians becoming increasingly dependent on clinical laboratory data for the diagnosis of disease and the monitoring of therapy, automation has become essential to processing the increasing workload in hospital clinical laboratories. Automated chemical analysis of biological fluid constituents has solved a great number of problems associated with conducting reliable and efficient analysis; it has, at the same time, however, has created its own dilemmas. Two logical alternatives to automation are either a much larger laboratory staff or much more judicial selection of appropriate laboratory tests by physicians. Since neither of these solutions is practical, however, the trend is toward advanced automated chemical analyzers that meet the needs of the present day analyst. Although automation provides a means by which an increased workload can be processed rapidly and reproducibly, limitations in the design of automated instruments make it difficult to achieve error free results of acceptable quality.
In clinical chemistry, the term "automation" implies the performance of analytical tests through mechanical or electronic control by an instrument with only minor involvement of an analyst. In the same context, partial automation refers to procedures in which the initial preparation of a specimen is done manually, but in which the analysis proceeds without human intervention. Presently, the vast majority of chemical analyzers require considerable manipulations by laboratory technicians and thus fall into the latter category. Illustrative of these are the allocation of a patient's fluid specimen for various types of analyses conducted either manually or in various instruments; appropriate dilution of specimen to meet the requirements of the various procedures; and complex book-keeping in order to keep track of the disposition and concentrating of the patient's specimen being analysed. On the other hand, totally manual analysis is also performed for specific tests not amenable to automated procedures, or where automated systems are either too expensive or cannot adequately be maintained. Since increased efficiency and reliability are necessary in the clinical laboratory, it is generally desirable to perform as many steps as possible without this manual intervention. Full automation reduces the possibility of human errors that arise from technicians making repetitive and boring manipulations, such as identifying, pipetting and analyzing a multitude of specimens.
Reliability and reproducibility of automated analytical test results in a clinical chemistry laboratory are essential to maintaining the accuracy of meaningful results to the clinician. Basically, the accuracy provided by automated chemical analyzers is no better than that obtained by carefully conducted conventional techniques; however, the precision (repeatability) is greatly increased. Measurement repeatability is often poor when manual analysis is employed as a consequence of some bias introduced into the analysis by an individual technologist. Furthermore, the ideal automated analytical system should employ the rapidity and simplicity of operation necessary for emergency "stat" tests, small volume specimens required for pediatric patients, and the high throughput required for routine analysis. Automated equipment that is properly designed offers greater reliability, less operative bias and more rapid evaluation of patient samples than is possible with manual methods.
Whether analysis is performed manually, automatically or uses a combination of the two, the basic steps common to the analysis cycle are: sample entry into the instrument, sample distribution with or without subsequent washout of the sample probe, reaction of sample with one or more reagents, followed by a quantitative determination of sample parameters and data presentation. Major drawbacks of currently used automated or partially automated chemical analyzers include: the need of highly trained laboratory personnel for the entry of sample and the operation of the instruments; specimen contamination and variability of results due to carry-over from adjacent specimens; a low throughput of samples to be analyzed; the lack of versatility to conduct many tests on the same specimen while retaining the capability of performing the same test on a multitude of different specimens in a short period of time; and the absence of satisfactory back-up or control systems to conveniently ensure the veracity of test results, and lack of positive sample identification. The lack of positive sample identification in a clinical chemistry laboratory is crucial since the miscorrelation of tests results with a patient's specimen can lead to incorrect diagnosis and consequently deprive the patient of proper therapy. Extensive manipulation of a patient's specimen considerably increases the chances of incorrectly assigning the wrong test results to that specimen. Although several automated instruments have addressed the problem of positive sample identification, none have adequately solved it.
Heretofore, automatic chemical analyzers have suffered from some or all of these problems and thus have not provided the clinician with the reliability and versatility necessary for the operation of modern clinical laboratories.